Fingering convection: an unforeseen physical process at work inside stars

Silvie VauclairUniversity of Toulouse

AbstractMain-sequence stars were thought to be well-known objects, but they still hide some surprises. An important process had been forgotten in previous studies, which may modify their internal structure and evolution in a non-negligible way. It is a type of double-diffusive convection, referred to as “thermohaline” or “fingering” convection. This occurs every time layers of heavy matter come upon lighter ones. It may happen inside stars due to the accumulation of heavy elements in some regions, as the result of atomic diffusion. It also happens in the case of accretion of heavy matter, coming from planetary disks or from stellar companions, and may lead to important extra-mixing effects. A similar phenomenon occurs at the surface of the white dwarfs which are surrounded by debris disks. I will discuss these processes, which have been studied in details using 3D simulations, and their importance for stellar structure and chemical composition.

21 April 2016, 13:15

Centro de AstrofísicaRua das Estrelas4150-762 Porto

Institute of Astrophysics and Space Sciences

Institute of Astrophysics and Space Sciences (IA) is a new but long anticipated research infrastructure with a national dimension. It embodies a bold but feasible vision for the development of Astronomy, Astrophysics and Space Sciences in Portugal, taking full advantage and fully realizing the potential created by the national membership of the European Space Agency (ESA) and the European Southern Observatory (ESO). IA resulted from the merging the two most prominent research units in the field in Portugal: the Centre for Astrophysics of the University of Porto (CAUP) and the Center for Astronomy and Astrophysics of the University of Lisbon (CAAUL). It currently hosts more than two-thirds of all active researchers working in Space Sciences in Portugal, and is responsible for an even greater fraction of the national productivity in international ISI journals in the area of Space Sciences. This is the scientific area with the highest relative impact factor (1.65 times above the international average) and the field with the highest average number of citations per article for Portugal.